Preparation of methyl vinyl ketone



Patented Mar. 13, 1945 PREPARATION OF METHYL VINYL KETONE William J. Hale, Midland, Mich., and Leland A. Underkofler, Ames, Iowa, assignors to National Agrol Company,.Inc., Washington, D. 0., a corporation of Delaware No Drawing. Application December 31, 1941, Serial No. 425,184

6 Claims. (Cl. zen-59.6)

This invention relates to a. catalytic process, and more especially to a process for preparing methyl vinyl ketone from acetyl methyl carbinol by dehydration.

Hitherto this ketone has been prepared from --such products as mono-vinyl-acetylene by the addition of a molecule of water or from beta acetyl ethyl alcohol by elimination of a molecule of water, and by other processes. In these processes it has always been necessary to operate with a sufficient quantity of water toprevent rapid polymerization of resulting ketone.

One of the objects of this invention is to provide a method of dehydrating acetyl methyl carblnol to prepare methyl vinyl ketone.

Still another object of this invention is to pro- This process is particularly'designed for usev in the conversion of acetyl methyl carbinol obtained by the mild oxidation of 2,3 butylene glycol which has been obtained directly from the fermentation of carbohydrates,-

The process comprises passing acetyl methyl carbinol vapors, heated within a range of from 250-400" C. and preferably within a range of 300-350 C. over an especially prepared catalyst which has been heated to approximately the same temperature. The dehydration step is car- In general the preparation of this activated dehydrative catalyst embodies the employment of a granular metal such as aluminum, beryllium, boron, magnesium, silicon, titanium or thorium, in contact with approximately 5 to its weight of tungstic acid, chromic acid or molybdic acid and the entire mass is triturated. After trituration the selected mixture is heated to approximately 600-700" C. or just under the point of endangering the reduction of the selected acidic oxide into its metal, as the catalyst will not work satisfactorily if it becomes sintered. The mass is then cooled to a temperature of about 350 C. and reduced in an atmosphere of hydrogen to eil'ect the reduction of the catalytic mass into its 'more active dehydrative state.

. heating and the reducing steps, and separate apbase metal and tungstic acid as the coating material, the core of the particle is metallic aluminum with an aluminum oxide outer surface in which is embedded a blue oxide of tungsten (W205) and aluminum tungstate.

The particular feature which distinguishes this new type of dehydrative catalyst from others heretofore known is the presence of a metallic core capable of serving as a reduction reserve 'ior the promotive agent, thus maintaining the ried on in the presence of an inert gas such as nitrogen.

In order to obtain a maximum yield, it is nec essary to use an especially selected catalyst. The catalyst used in this process is disclosed in the latter in a state of highest possible activity and thereby contributing to the masking of any dehydrogenative characteristics likely to be displayed by the basic metallic oxides present. A

definite and stable equilibrium between the component parts of this improved catalytic mass 'is indicated by the absence of caking, disintegration and sintering through many hours of its continuous service.

In this application the term base metal is limited to aluminum, beryllium, boron, magne sium, silicon, titanium or thorium and their chemical equivalents, and the term metallic oxide having strong dehydrative properties includes only the promotive reduced oxides of chromium,molybdenum, and tungsten' "acidic Although acetyl methyl carbinol from any source may be used as the starting material in butylene glycol obtained from the fermentation disclosed in the co-pending applications of Leo M. Christensen, Serial No. 383,051, filed March 12, 1941, and Serial No. 383,052, filed March 12,

1941. In these applications is disclosed a method of fermenting carbohydrates after inoculation with aerobacters to produce a mixture containing 2,3 butylene glycol and water. Therefore,

by means oLthe present process a product containing only water as van impurity can be obtained from acetylmethyl carbinol produced from low priced sugar solutions.

In this connection it may be necessary to remove some of the water contained in the fermentation processes described in the above entitled applications. However, it is usually not necessary to remove more than a slight percentage of water due to the fact that the present process requires the presence of approximately 20% by Weight of water to obtaina maximum yield of methyl vinyl ketone. Therefore, the residual menstruum resulting from the fermentation may be used directly in 'the'present process after mild oxidation, without the necessity of removing more than a fraction of the water, and a starting material for the present process or the methyl vinyl ketone may be distilled out of the mixture with steam preferably under reduced pressure.

The following examples are given to illustrate the difference between the yields obtained by use of the special catalysts and that obtained under ordinary conditions Example I grams of acetyl methyl carbinol to which was added two grams of water was heatedto 300' C. and passed in the presence of nitrogen over .10 grams of an aluminum oxide catalyst and held -at 360 C. At the end of the first run, there was obtained in the receiver 9.4 grams of oil containing 1.9 grams of methyl vinyl ketone and 4.5 grams of acetyl methyl carbinol unacted upon. This represents a conversion of about 62% of the theoretical.

distilled directly therefrom. However, it is to be understood that acetyl methyl carbinol from any source may be used in the process and a high yield of methyl vinyl ketone will be produced.

In practicing the invention the selected acetyl methyl carbinol is diluted with approximately 20% of its weight of water and heated to a temperature of from 250-400? C., and preferably within a range of from 300-350 C., and these vapors together with an inert gas are then passed over the selected catalyst which has been heated to the same temperature. This temperature is maintained during the catalytic reaction.

As previously mentioned, it has. been found to be preferable to conduct the dehydration within the range of from 250-400" C., and. particularly within the range of from 300350 C. Moreover, it has been found desirable to activate the catalyst by subjecting it to a stream of hydrogen beconnection, it should be noted that alumina or mixtures of alumina with chromic oxides or been found that a higher yield of methyl vinyl ketone can be obtained than is possible when ordinary catalysts are selected. In this connection experiments have shown that on the first run over the preferred catalyst, yields of methyl vinyl ketone of approximately 80 85 percent have been consistently obtained. Moreover, the end product'discloses that the conversion is conducted without any trace of decomposition. The methyl vinyl ketone and the acetyl methyl carbinol unacted upon, can be readily separated from the water by salting out with potassium carbonate;

Example II Under the same conditions as those described in Example I, 10 grams of acetyl methyl car-' binol mixed with two grams of water were heated to 300 C. and passed over 10 grams of chromic oxide and held at 360 C. The product resulting from the first run of this mixture of the catalyst consisted of 9.2 grams of oil containing 4.2 grams of methyl vinyl lretone representing a conversion of 53% of the theoretical.

Example III Under the same conditions as those described in Example I, 10 grams of acetyl methyl carbinol together with two grams of water were passed over 10 grams of a mixture of aluminum oxide and tungstic oxide, previously reduced in an atmosphere of hydrogen at 350 C. and held at this point. The oily product obtained amounted to 9.4 grams containing'5.8 grams of methyl vinyl ketone, thus representing a conversion of 73% of the theoretical.

Example IV 10 grams of acetyl methyl carbinol together with two grams of water were heated to 300 C. and in the presence of nitrogen passed over 10 grams of our specifically described active catalyst which here was formed of aluminum-aluminum oxide, and tungstic oxide prepared in the manner previously described and held at 300 C. The resulting oily product upon the first pass amounted to 6.5 grams of methyl vinyl ketone and 2.9 grams of unconverted acetyl methyl carbinol. This corresponds to a conversion of about 82% of the theoretical.

It is believed apparent from the above description that we have provided a process of obtaining an increased yield of methyl vinyl ketone with lowest amount of contamination by means of dehydration.- It is also apparent that various changes can be made by one skilled in the art, without departing from the scope of the invention.

We claim:

1. A process for producing methyl vinyl ketone comprising heating a mixture of acetyl methyl carbinol and water to a temperatureof from -250 to 400 C., passing the resulting vapors together with an inert gas over a dehydration catalyst which has been heated to a temperature of from 250 to 400 C., and maintaining this temperature during the catalytic reaction.

2. A process for producing methyl vinyl ketone comprising heating a mixture of acetyl methyl carbinol and water to a temperature of from 250 aa'ms'r! it to 400' C., passing the resulting vapors together with an inert gas over a dehydration catalyst which has been heated to the same temperature, and maintaining this temperature during the catalytic reaction.

3. A process for producing methyl vinyl ketone comprising heating a mixture of acetyl methyl carbinol and water to a temperature of from'300 to 350 C., passing the resultingvapors together with an inert gas over a dehydration catalyst which has been heated to the same temperature, and maintaining this temperature during the catalytic reaction.

4. A process for producing methyl vinyl ketone comprising heating acetyl methyl carbinol diluted with approximately 20% of its weight of water ing this temperature during the catalytic reaction.

5. A process for producing methyl vinyl ketone been heated to the same temperature, and maintaining thistemperature during the catalytic reaction. v

6. A process for producing methyl vinyl ketone comprising heating acetyl methyl carbinol diluted with approximately 20% of its weight of water to a temperature of from 300 to 350 C.,

passing the resulting vapors together "with an inert gas over a dehydration catalyst which has been heated to the same temperature, and maintaining this temperature during the catalytic reaction, said catalyst comprising non-sintered particles composed of a base metal core embedded in an irregular layerof itsown oxide which is coated with a reduced acidic oxide havingdehydrative properties.

WILLIAM J. HALE.

LELAND A. UNDERKOFLER. 

